Production well assembly for in situ combustion



R. M. JORDA 3,160,208

PRODUCTION WELL ASSEMBLY FOR IN SITU COMBUSTION Dec. 8, 1964 Filed Oct. 6, 1961 \f 4 q 4. 1 1 1 4 4 4 4 Z. 4.. /4

INVENTORI R. M. JORDA BY: IS AGENT United States Patent 3,160,2tl3 PRQDUCTTON WELL ASEMBL FGR lN @lTU (IUMBUSTEGN Robert M. .lor-da, Houston, Tex, assignor to hell @il Company, New York, N.Y., a corporation of lilelaware Filed Get. 6, B61, Ser. No. 143,459 5 (Ilairns. (ill. 166-457) The present invention relates to a well assembly and pertains more particularly to a production well assembly for use in underground combustion system for recovering petroleum products from earth formations.

An in-situ combustion thermal recovery process, commonly known as underground combustion, is a wellknown process for recovering oil or other petroleum products from underground formations, which products would otherwise be unrecoverable by normal producing means.

, In this thermal recover-y method, air or other oxygencontaining gases are injected into an oil-containing formation through an injection well at a rate suiiicient to carry out a combustion in the oil-containing zone. Continued injection of gas into the injection well forces heated fluids in the formation, and also the by-products of the cornbustion, outwardly away from the injection well and toward one or more production wells through which the gases and heated liquids may be produced to the surface.

To date, the producing wells of an in-situ underground combustion or fire flood have experienced failure of equipment because temperatures attained within the borehole have caused melting or other unfavorable deterioration of the metal liner or casing in the borehole and similar damage to production strings therein.

The significant cause of failure of pipe strings, tubing strings and production strings within a well has been excessive heat. In one field experiment, the temperatures of about 1800 P. which occurred were suflicient to cause failure of tubing, casing and scavenging lines. Temperatures have been measured in actual and simulated reservoirs and in boreholes during many experiments and the field studies of in-situ combustion. The evidence to date suggests that the temperatures in the reservoir are of the order of 600 F. to a maximum of 1000 F., averaging 8%" F. Both laboratories and field studies have shown that a combustion front forms in a very narrow zone of small dimensions in the reservoir, and that the combustion takes place between oxygen in the injected air and only a portion of the reservoir oil. No actual flame is formed because the pore channels in the matrix of the reservoir are too small. instead, a llarneless combustion reaction takes place between the oil and the oxygen with suflicient energy to be self sustaining as long as a sufiicient flow of oxygen is maintained.

When the burning and constantly moving combustion front reaches the producing well, however, sustained burning can occur within the borehole, and temperatures of the order of 2200 F. accompanied by flaming, have been observed in the laboratory and in the field. It is at this time that injury of the production well equipment downhole may take place because of the high temperatures encountered. i

The Well bore serves as a chamber in which intimate mixing of oil and oxygen occurs, and the oxidation of the oil may approach its maximum rate with associatedhigh temperatures. The maximum temperature in-any producing well is determined by (a) the rate of heat generation within the well, which is governed by the rate of flow of combustible hydrocarbons and oxygen into the Well and the temperature at which the reaction occurs, and (b) the rate of heat transfer away from the well bore. The occurrence of flame in the open well bore has been associated with these conditions. The flaming aggravates the problem of equipment damage within the well as numerous hot spots, which are destructive to most metals, are formed in the downhole equipment.

It is therefore a primary object of the present invention to provide a production well assembly for use in an underground combustion system whereby the high temperatures generally encountered have no deleterious afiect on a downhole well equipment employed.

A further object of the present invention is to provide a production well assembly for use in underground combustion system whereby the hot produced gases are cooled prior to being discharged from the top of the well.

Another object of the present invention is to provide production well equipment for an underground combustion system whereby injury to the well casing is precluded even though combustion takes place within the well itself.

These and other objects of this invention will be understood from the following description taken with reference to the drawing which schematically illustrates a Well assembly in accordance with the present invention taken in longitudinal section while being positioned in a well bore.

Referring to the drawing, a well 11 is illustrated as traversing a production zone 12 of an underground formation. A string of well casing 13 is positioned in a well 11 and extends downwardly into or through the oilbearing formation 32 in which an underground combustion is to take. place. If desired, the well casing string 13 may be cemented in the borehole 11 at a point 14 above the production Zone 12. Although the well casing 13 and the other pipe or tubing strings to be described in the present invention are diagrammatically illustrated as being unitary structures, it is to be understood thatthey generally consist of a plurality of pipe sections connected together in any suitable manner well-known to the art, as by screw threads.

Concentrically positioned within the well casing 13 and extending at least through the production zone 12 of the well 11 is a pipe string, casing or metal liner of smaller diameter than that of the well casing 13. The well casing 13 and the inner pipe string 15 are closed in a fluidtight manner by suitable closure means, diagrammatically represented by plate elements 16 and 17, although it is to be understood that the lowermost closure element 1.6 may be any suitable downhole closure element for closing pipes while the upper closure element 17 may be in the form of any wellhead known to the art. Closing of the top and bottom of the well casing 13 and the pipe string 15 forms an annular space 17 which is provided with a suitable discharge port 18 through the wall of the well assembly above the surface of the ground 19. Thus, a cooling water jacket is formed on the well casing which extends at least the height of the production zone 12.

A plurality of laterall-extending conduits 21 extend through the walls of the pipe string 15 and well casing 13 in a fiuid'tight manner and are in open communication between the interior of the pipe string 15 and the space outside the well casing 13 at a point adjacent the formation 12 to be produced. Extending down through the annular space 17 between the pipe string 15 and the well casing 13 from a point above the upper closure 17 down to a point near the lower end of the annular space 17 is a small-diameter pipe string or conduit 22. Thus, by use of the small pipe string 22, cooling water can be pumped down to the bottom of the annular space 17 from whence it flows upwardly to be discharged through the port 18 above ground.

In the event that mainly gaseous products are being discharged from the production formation 12 into the well, the hot produced gases may be allowed to flow up the inner pipe string 15 to be discharged out port or conduit 23 which extends through the upper closure 1'7. However, since in most installations both heated liquid and the gases are produced from the formation 12 into the well, the well assembly is preferably provided with an inner production conduit 24 which extends from a point near the bottom of the well up through the pipe string 15 and out through the closure 17.

Thus, during the carrying out of an underground combustion, the heated oil from the producing formation 12 may flow through the lower lateral conduits 21 extending through the well casing 13 and pipe string 15 into the bottom of the pipe string 15 from whence it may flow or be lifted by suitable pumping apparatus (not shown) up the production conduit 24 and out of the well. At the same time gases from the producing formation may flow through the upper lateral conduits or ports 21, through the well casing 13 and inner pipe string 15 to pass up the annular space 25 between the pipe string 15 and the production conduit 24. At the top of the annular space 24 the gases would be discharged through conduit 23. Throughout the period at which the underground combustion was producing fluid into the well, a suitable cooling fluid such as water would be pumped down the smaller diameter pipe string 22 to the bottom of the annular space 17 between the well casing 13 and the pipe string 15. Thus, the well casing adjacent the hot producing zone 12 would be continually cooled,thus preventing damage to the well casing. At the same time the inner pipe string 15 would be cooled thus cooling the hot gases as they were being produced upwardly through the inner pipe string 15 to the top of the well.

I claim as my invention:

1. A production well assembly for use in an underground combustion system for recovering petroleum products from earth formations, said assembly comprising a Well casing extending into a well to a point adjacent an oil-bearing formation to be produced, means fixedly positioning said casing in said well, pipe string mounted within said well casing and extending from the top thereof down past that portion of the casing adjacent the formation to be produced whereby an annular space is formed between said pipe string and said casing, first closure means closing the pipe string and the annular space between said pipe string and said casing at a point below the formation to be produced, conduit means extending through the walls of said pipe string and said casing in communication between the interior of said pipe string and the exterior of said well casing at a point adjacent said formation to be produced, second closure means closing the pipe string and the annular space between said pipe string and the casing at the top thereof, cooling water conduit means extending from the top of the well and down through the annular space between said casing and said pipe string to a point near the lower portion of said annular space, and conduit means in said well and extending out the top thereof for producing hydrocarbons therefrom.

2. A production well assembly for use in an underground combustion system for recovering petroleum prodacts from earth formations, said assembly comprising a well casing extending into a well to a point adjacent an oil-bearing formation to be produced, means fixedly positioning said casing in said well, a pipe string mounted within said well casing at least over that portion of the casing adjacent the formation to be produced whereby an annular space is formed between said pipe string and said casing, first closure means closing the pipe string and the annular space between said pipe string and said casing at a point near the bottom of the formation to be produced, a plurality of laterally-extending conduit means each extending through the walls of said pipe string and said casing in open communication between the interior of said pipe string and the exterior of said Well casing at a point adjacent said formation to be produced, second closure means closing the pipe string and the annular space between said pipe string and the casing at a point above the formation to be produced, cooling water conduit means extending from the top of the well and down through the annular space between said casing and said pipe string to a point near the lower portion of said annular space and conduit means in said well and extending out of the top thereof for producing hydrocarbons therefrom.

3. A production well assembly for use in an underground combustion system for recovering petroleum prod ucts from earth formations, said assembly comprising a well casing extending into a well to a point adjacent an oil-bearing formation to be produced, means fixedly positioning said casing in said well, a large-diameter pipe string concentrically mounted within said well casing and extending from the top thereof down past that portion of the casing adjacent the formation to be produced whereby an annular space is formed'between said pipe string and said casing, first closure means closing the pipe string and the annular space between said pipe string and said casing at a point below the formation to be produced, a plurality of laterally-extending conduit means each ex tending through the walls of said pipe string and said casing in open communication between the interior of said pipe string and the exterior of said well casing at a point adjacent said formation to be produced, second closure means closing the pipe string and the annular space between said pipe string and the casing at the top thereof, cooling water conduit means extending from the top of the well and down through the annular space between said casing and said pipe string to a point near the lower portion of said annular space, and a production conduit extending from the top of the well and into said pipe string to a point near the bottom thereof.

4. A production well assembly for use in an underground combustion system for recovering petroleum products from earth formations, said assembly comprising a well casing extending into a well to a point adjacent an oil-bearing formation to be produced and being fixedly positioned in said well, cementing means securing said well casing in said well at a point above the formation to be produced, a large-diameter pipe string concentrically mounted within said well casing and extending from the top thereof down past that portion of the casing adjacent the formation to be produced whereby an annular space is formed between said pipe string and said casing, first closure means closing the pipe string and the annular space between said pipe string and said casing at a point below the formation to be produced, a plurality of laterally-extending conduit means each extending through the walls of said pipe string and said casing in open communication between the interior of said pipe string and the exterior of said well casing at a point adjacent said formation to be produced, second closure means closing the pipe string and the annular space between said pipe string and the casing at the top thereof, cooling water conduit 'means extending from the top of the well and through said second closure means down through the annular space between said casing and said pipe string to a point near the lower portion of said annular space, and a production conduit extending from the top of the well through said second closure means and into said pipe string to a point near the bottom thereof.

5. A production well head assembly for use in an underground combustion system for recovering petroleum products from earth formations, said assembly comprising a well casing extending into a well to a point adjacent an oil bearing formation to be produced, means fixedly positioning said casing in said well, a cooling water jacket formed around the inside of said Well casing at least over that portion of the casing adjacent the formation to be produced whereby an annular space is formed around the inside of the casing which forms one wall of said cooling water jacket, said casing having port means in open communication between the interior and the exterior of the well casing at a point adjacent said formation to be produced, closure means closing the casing at the top thereof, conduit means in said well and extending out of the top thereof for producing hydrocarbons therefrom,

and cooling water conduit means extending from the top of the well alongside said well casing to said Water jacket for circulating water therein.

References Cited in the file of this patent UNITED STATES PATENTS 

5. A PRODUCTION WELL HEAD ASSEMBLY FOR USE IN AN UNDERGROUND COMBUSTION SYSTEM FOR RECOVERING PETROLEUM PRODUCTS FROM EARTH FORMATIONS, SAID ASSEMBLY COMPRISING A WELL CASING EXTENDING INTO A WELL TO A POINT ADJACENT AN OIL BEARING FORMATION TO BE PRODUCED, MEANS FIXEDLY POSITIONING SAID CASING IN SAID WELL, A COOLING WATER JACKET FORMED AROUND THE INSIDE OF SAID WELL CASING AT LEAST OVER THAT PORTION OF THE CASIG ADJACENT THE FORMATION TO BE PRODUCED WHEREBY AN ANNULAR SPACE IS FORMED AROUND THE INSIDE OF THE CASING WHICH FORMS ONE WALL OF SAID COOLING WATER JACKET, SAID CASING HAVING PORT MEANS IN OPEN COMMUNICATION BETWEEN THE INTERIOR AND THE EXTERIOR OF THE WELL CASING AT A POINT ADJACENT SAID FORMATION TO BE PRODUCED, CLOSURE MEANS CLOSING THE CASING AT THE TOP THEREOF, CONDUIT MEANS IN SAID WELL AND EXTENDING OUT OF THE TOP THEREOF FOR PRODUCING HYDROCARBONS THEREFROM, AND COOLING WATER CONDUIT MEANS EXTENDING FROM THE 